1. Field of the Invention
The present invention relates to a light emitting device.
2. Description of the Related Art
Examples of conventional light emitting devices include those disclosed in JP-A-7-15046 and JP-A-2007-184377. The conventional light emitting devices disclosed in these documents are described below.
FIGS. 55 and 56 illustrate the light emitting device disclosed in JP-A-7-15046. The illustrated light emitting device 9A includes a substrate 91, a first conductor pattern 92, a second conductor pattern 93, a light emitting element 94 and a wire 95.
The front surface 91a of the substrate 91 is formed with a recess 911, and a recess 912 which is larger than the recess 911. The recess 911 is formed in the bottom surface 912a of the recess 912. The side surface 911b of the recess 911 is a reflective surface which reflects the light emitted from the light emitting element 94. The first conductor pattern 92 extends from the front surface 91a of the substrate 91 onto the bottom surface 911a of the recess 911. The second conductor pattern 93 extends from the front surface 91a of the substrate 91 onto the bottom surface 912a of the recess 912. The light emitting element 94 is disposed on the bottom surface 911a of the recess 911 and electrically connected to an end of the first conductor pattern 92. The wire 95 is connected to the light emitting element 94 and to the second conductor pattern 93.
In the above-described light emitting device 9A, it may be desired to increase the intensity of light emitted toward the front while maintaining a desired directivity angle. As a means to achieve this, it may be considered to increase the area of the reflective surface (side surface) 911b by increasing the depth of the recess 911. However, since the recess 911 is formed in the bottom surface 912a of the recess 912, the depth of the recess 911 can be increased only within a limited range. As a result, the area of the side surface 911b may not be increased sufficiently.
FIG. 57 illustrates a light emitting device (an LED module) disclosed in JP-A-2007-184377. The illustrated light emitting element 9B includes an LED element 581, a case 582 having a main surface 583, a first lead 586 to which the LED element 581 is bonded, and a second lead 589 connected to the LED element 581 by way of a wire 593. The main surface 583 is formed with a recess 585 including a reflective surface 584. The first lead 586 includes an inner lead portion 587 extending from one side of the case 582 to near the center of the recess 585. The inner lead portion 587 includes a leading end (rectangular die pad portion) to which the LED element 581 is bonded to face the reflective surface 584. Specifically, the LED element 581 is bonded with a conductive adhesive, with its four corners positioned correspondingly to the corners of the die pad portion, respectively. The second lead 589 includes an inner lead portion 590 extending from the other side of the case 582 to near the inner lead portion 587 of the first lead 586. The recess 585 is filled with light-transmitting resin 592.
In manufacturing the LED module 9B, the light-transmitting resin 592 in the liquid state is loaded into the recess 585. Thereafter, as the light-transmitting resin 592 hardens, the inner lead portions 587, 590 of the first and the second leads 586, 589 are bonded to the surface of the light-transmitting resin 592. The outer lead portions 588 and 591 are bent by forming to extend from the main surface 583 along the side surfaces and then along the bottom surface of the case 582. Of the outer lead portions 588 and 591 bent in this way, the portions which extend, along the bottom surface of the case 582 are used as electrode terminals.
The light emitted from the LED element 581 is reflected at the reflective surface 584 of the recess 585, passes through the light-transmitting resin 592, and is then emitted to the outside of the case 582. In this process, the inner lead portion 587 and 590 act as a light shielding portion which blocks the light traveling toward the outside. Therefore, in terms of enhancing the brightness, it is preferable that the inner lead portions 587 and 590 are as narrow as possible. In bonding the LED element 581 to the die pad portion of the first lead 586 by way of a conductive adhesive, the conductive adhesive tends to be pressed out of the four sides of the LED element 581. Thus, to secure a sufficient space around the LED element 581, it is demanded that each side of the die pad portion has a large dimension. However, this demand is incompatible with the demand for a reduction in width of the inner lead portion 587.
Further, when the inner lead portion 587 and 590 of the LED module 9B is narrow, the surface area of the portion which is in contact with the light-transmitting resin 592 is small, which leads to deteriorated bonding strength to the light-transmitting resin 592. In such a case, there is a risk that the inner lead portions 587 and 590 separate from the light-transmitting resin 592 due to the elastic recovery of the outer lead portions 588 and 591 which have been bent by forming.